Ultrastructural studies have shown that the spermatozoa of certain parasitic nematodes acquire motility and undergo structural alterations following deposition in the female uterus. More recent evidence indicates that these physiological and morphological changes are strongly influenced by male sex accessory gland secretions which, along with the sperm, are transferred to the female during copulation. The objectives of the present study are to: 1) determine the chemical nature of the sperm activating substance present in male accessory glands utilizing ammonium sulfate precipitation and sodium dodecyl sulfate-polyacrylamide electrophoresis, 2) describe the precise morphological and chemical alterations which occur at the sperm membrane level during the activation process. Concanavalin A and other phytoagglutinins as well as colloidal iron hydroxide, colloidal lanthanum, ruthenium red and cationic ferritin will be utilized to determine the nature, density, and distribution of carbohydrate rich residues present on the plasmalemma of both unactivated and activated cells, 3) attempt to extract and purify myosin from activated nematode sperm using potassium iodide procedures to determine whether the pseudopods generate motility utilizing a sliding filament mechanism or are modified acrosomal processes which lack myosin and 4) determine the requirements for the in vitro fertilization of nematode gametes. This objective will be initiated by becoming familiar with the techniques used for the in vitro fertilization of mammalian and echinoderm eggs in other laboratories. The proposed studies will be used to determine if the alterations of in utero nematode spermatozoa are a necessary preliminary to fertilization and are therefore comparable in some respects to the capacitation phenomenon reported in mammalian spermatozoa. This information will be particularly useful both in determining how zygote formation is accomplished in species having acrosomeless spermatozoa and in formulating a broader concept of the capacitation phenomenon which is relatively unknown in invertebrate organisms.